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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Tue Nov 27 09:11:42 2007" /> 9 <meta name="created" content="Sun Dec 9 20:30:11 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
… …
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
36<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> 37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
37<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li> 38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
38<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li> 39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
39<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
40</ul> 42</ul>
41</li> 43</li>
42<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
43<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
44<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
45<li><a href="#EMBEDDING">EMBEDDING</a> 48<li><a href="#EMBEDDING">EMBEDDING</a>
46<ul><li><a href="#FILESETS">FILESETS</a> 49<ul><li><a href="#FILESETS">FILESETS</a>
47<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
48<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
49<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
57<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
58</li> 61</li>
59</ul><hr /> 62</ul><hr />
60<!-- INDEX END --> 63<!-- INDEX END -->
61 64
62<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
63<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
64<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
65 68
66</div> 69</div>
67<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
68<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
69<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
70 73
71</pre> 74</pre>
72 75
73</div> 76</div>
74<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
75<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
76<p>Libev is an event loop: you register interest in certain events (such as a 127<p>Libev is an event loop: you register interest in certain events (such as a
77file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
78these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
79<p>To do this, it must take more or less complete control over your process 130<p>To do this, it must take more or less complete control over your process
80(or thread) by executing the <i>event loop</i> handler, and will then 131(or thread) by executing the <i>event loop</i> handler, and will then
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83watchers</i>, which are relatively small C structures you initialise with the 134watchers</i>, which are relatively small C structures you initialise with the
84details of the event, and then hand it over to libev by <i>starting</i> the 135details of the event, and then hand it over to libev by <i>starting</i> the
85watcher.</p> 136watcher.</p>
86 137
87</div> 138</div>
88<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 139<h1 id="FEATURES">FEATURES</h1>
89<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
90<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 141<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
91kqueue mechanisms for file descriptor events, relative timers, absolute 142BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
92timers with customised rescheduling, signal events, process status change 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
93events (related to SIGCHLD), and event watchers dealing with the event 144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
94loop mechanism itself (idle, prepare and check watchers). It also is quite 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
146(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
147watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
148<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
149file watchers (<code>ev_stat</code>) and even limited support for fork events
150(<code>ev_fork</code>).</p>
151<p>It also is quite fast (see this
95fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 152<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
96it to libevent for example).</p> 153for example).</p>
97 154
98</div> 155</div>
99<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 156<h1 id="CONVENTIONS">CONVENTIONS</h1>
100<div id="CONVENTIONS_CONTENT"> 157<div id="CONVENTIONS_CONTENT">
101<p>Libev is very configurable. In this manual the default configuration 158<p>Libev is very configurable. In this manual the default configuration will
102will be described, which supports multiple event loops. For more info 159be described, which supports multiple event loops. For more info about
103about various configuration options please have a look at the file 160various configuration options please have a look at <strong>EMBED</strong> section in
104<cite>README.embed</cite> in the libev distribution. If libev was configured without 161this manual. If libev was configured without support for multiple event
105support for multiple event loops, then all functions taking an initial 162loops, then all functions taking an initial argument of name <code>loop</code>
106argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 163(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
107will not have this argument.</p>
108 164
109</div> 165</div>
110<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 166<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
111<div id="TIME_REPRESENTATION_CONTENT"> 167<div id="TIME_REPRESENTATION_CONTENT">
112<p>Libev represents time as a single floating point number, representing the 168<p>Libev represents time as a single floating point number, representing the
113(fractional) number of seconds since the (POSIX) epoch (somewhere near 169(fractional) number of seconds since the (POSIX) epoch (somewhere near
114the beginning of 1970, details are complicated, don't ask). This type is 170the beginning of 1970, details are complicated, don't ask). This type is
115called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 171called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
116to the <code>double</code> type in C, and when you need to do any calculations on 172to the <code>double</code> type in C, and when you need to do any calculations on
117it, you should treat it as such.</p> 173it, you should treat it as such.</p>
118 174
119
120
121
122
123</div> 175</div>
124<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 176<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
125<div id="GLOBAL_FUNCTIONS_CONTENT"> 177<div id="GLOBAL_FUNCTIONS_CONTENT">
126<p>These functions can be called anytime, even before initialising the 178<p>These functions can be called anytime, even before initialising the
127library in any way.</p> 179library in any way.</p>
128<dl> 180<dl>
129 <dt>ev_tstamp ev_time ()</dt> 181 <dt>ev_tstamp ev_time ()</dt>
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142version of the library your program was compiled against.</p> 194version of the library your program was compiled against.</p>
143 <p>Usually, it's a good idea to terminate if the major versions mismatch, 195 <p>Usually, it's a good idea to terminate if the major versions mismatch,
144as this indicates an incompatible change. Minor versions are usually 196as this indicates an incompatible change. Minor versions are usually
145compatible to older versions, so a larger minor version alone is usually 197compatible to older versions, so a larger minor version alone is usually
146not a problem.</p> 198not a problem.</p>
147 <p>Example: make sure we haven't accidentally been linked against the wrong 199 <p>Example: Make sure we haven't accidentally been linked against the wrong
148version:</p> 200version.</p>
149<pre> assert ((&quot;libev version mismatch&quot;, 201<pre> assert ((&quot;libev version mismatch&quot;,
150 ev_version_major () == EV_VERSION_MAJOR 202 ev_version_major () == EV_VERSION_MAJOR
151 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 203 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
152 204
153</pre> 205</pre>
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183recommended ones.</p> 235recommended ones.</p>
184 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 236 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
185 </dd> 237 </dd>
186 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
187 <dd> 239 <dd>
188 <p>Sets the allocation function to use (the prototype is similar to the 240 <p>Sets the allocation function to use (the prototype is similar - the
189realloc C function, the semantics are identical). It is used to allocate 241semantics is identical - to the realloc C function). It is used to
190and free memory (no surprises here). If it returns zero when memory 242allocate and free memory (no surprises here). If it returns zero when
191needs to be allocated, the library might abort or take some potentially 243memory needs to be allocated, the library might abort or take some
192destructive action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
193 <p>You could override this function in high-availability programs to, say, 246 <p>You could override this function in high-availability programs to, say,
194free some memory if it cannot allocate memory, to use a special allocator, 247free some memory if it cannot allocate memory, to use a special allocator,
195or even to sleep a while and retry until some memory is available.</p> 248or even to sleep a while and retry until some memory is available.</p>
196 <p>Example: replace the libev allocator with one that waits a bit and then 249 <p>Example: Replace the libev allocator with one that waits a bit and then
197retries: better than mine).</p> 250retries).</p>
198<pre> static void * 251<pre> static void *
199 persistent_realloc (void *ptr, long size) 252 persistent_realloc (void *ptr, size_t size)
200 { 253 {
201 for (;;) 254 for (;;)
202 { 255 {
203 void *newptr = realloc (ptr, size); 256 void *newptr = realloc (ptr, size);
204 257
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221indicating the system call or subsystem causing the problem. If this 274indicating the system call or subsystem causing the problem. If this
222callback is set, then libev will expect it to remedy the sitution, no 275callback is set, then libev will expect it to remedy the sitution, no
223matter what, when it returns. That is, libev will generally retry the 276matter what, when it returns. That is, libev will generally retry the
224requested operation, or, if the condition doesn't go away, do bad stuff 277requested operation, or, if the condition doesn't go away, do bad stuff
225(such as abort).</p> 278(such as abort).</p>
226 <p>Example: do the same thing as libev does internally:</p> 279 <p>Example: This is basically the same thing that libev does internally, too.</p>
227<pre> static void 280<pre> static void
228 fatal_error (const char *msg) 281 fatal_error (const char *msg)
229 { 282 {
230 perror (msg); 283 perror (msg);
231 abort (); 284 abort ();
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237</pre> 290</pre>
238 </dd> 291 </dd>
239</dl> 292</dl>
240 293
241</div> 294</div>
242<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 295<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
243<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 296<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
244<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 297<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
245types of such loops, the <i>default</i> loop, which supports signals and child 298types of such loops, the <i>default</i> loop, which supports signals and child
246events, and dynamically created loops which do not.</p> 299events, and dynamically created loops which do not.</p>
247<p>If you use threads, a common model is to run the default event loop 300<p>If you use threads, a common model is to run the default event loop
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276<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
277override the flags completely if it is found in the environment. This is 330override the flags completely if it is found in the environment. This is
278useful to try out specific backends to test their performance, or to work 331useful to try out specific backends to test their performance, or to work
279around bugs.</p> 332around bugs.</p>
280 </dd> 333 </dd>
334 <dt><code>EVFLAG_FORKCHECK</code></dt>
335 <dd>
336 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
337a fork, you can also make libev check for a fork in each iteration by
338enabling this flag.</p>
339 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
340and thus this might slow down your event loop if you do a lot of loop
341iterations and little real work, but is usually not noticeable (on my
342Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
343without a syscall and thus <i>very</i> fast, but my Linux system also has
344<code>pthread_atfork</code> which is even faster).</p>
345 <p>The big advantage of this flag is that you can forget about fork (and
346forget about forgetting to tell libev about forking) when you use this
347flag.</p>
348 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
349environment variable.</p>
350 </dd>
281 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
282 <dd> 352 <dd>
283 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 353 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
284libev tries to roll its own fd_set with no limits on the number of fds, 354libev tries to roll its own fd_set with no limits on the number of fds,
285but if that fails, expect a fairly low limit on the number of fds when 355but if that fails, expect a fairly low limit on the number of fds when
… …
367 <dd> 437 <dd>
368 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 438 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
369always distinct from the default loop. Unlike the default loop, it cannot 439always distinct from the default loop. Unlike the default loop, it cannot
370handle signal and child watchers, and attempts to do so will be greeted by 440handle signal and child watchers, and attempts to do so will be greeted by
371undefined behaviour (or a failed assertion if assertions are enabled).</p> 441undefined behaviour (or a failed assertion if assertions are enabled).</p>
372 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 442 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
373<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 443<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
374 if (!epoller) 444 if (!epoller)
375 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 445 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
376 446
377</pre> 447</pre>
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413 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
414 <dd> 484 <dd>
415 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 485 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
416<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 486<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
417after fork, and how you do this is entirely your own problem.</p> 487after fork, and how you do this is entirely your own problem.</p>
488 </dd>
489 <dt>unsigned int ev_loop_count (loop)</dt>
490 <dd>
491 <p>Returns the count of loop iterations for the loop, which is identical to
492the number of times libev did poll for new events. It starts at <code>0</code> and
493happily wraps around with enough iterations.</p>
494 <p>This value can sometimes be useful as a generation counter of sorts (it
495&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
496<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
418 </dd> 497 </dd>
419 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
420 <dd> 499 <dd>
421 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 500 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
422use.</p> 501use.</p>
… …
450one iteration of the loop. This is useful if you are waiting for some 529one iteration of the loop. This is useful if you are waiting for some
451external event in conjunction with something not expressible using other 530external event in conjunction with something not expressible using other
452libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 531libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
453usually a better approach for this kind of thing.</p> 532usually a better approach for this kind of thing.</p>
454 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 533 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
534<pre> - Before the first iteration, call any pending watchers.
455<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
456 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
457 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
458 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
459 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
460 - Calculate for how long to block. 540 - Calculate for how long to block.
461 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
… …
470 be handled here by queueing them when their watcher gets executed. 550 be handled here by queueing them when their watcher gets executed.
471 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 551 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
472 were used, return, otherwise continue with step *. 552 were used, return, otherwise continue with step *.
473 553
474</pre> 554</pre>
475 <p>Example: queue some jobs and then loop until no events are outsanding 555 <p>Example: Queue some jobs and then loop until no events are outsanding
476anymore.</p> 556anymore.</p>
477<pre> ... queue jobs here, make sure they register event watchers as long 557<pre> ... queue jobs here, make sure they register event watchers as long
478 ... as they still have work to do (even an idle watcher will do..) 558 ... as they still have work to do (even an idle watcher will do..)
479 ev_loop (my_loop, 0); 559 ev_loop (my_loop, 0);
480 ... jobs done. yeah! 560 ... jobs done. yeah!
… …
499example, libev itself uses this for its internal signal pipe: It is not 579example, libev itself uses this for its internal signal pipe: It is not
500visible to the libev user and should not keep <code>ev_loop</code> from exiting if 580visible to the libev user and should not keep <code>ev_loop</code> from exiting if
501no event watchers registered by it are active. It is also an excellent 581no event watchers registered by it are active. It is also an excellent
502way to do this for generic recurring timers or from within third-party 582way to do this for generic recurring timers or from within third-party
503libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 583libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
504 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 584 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
505running when nothing else is active.</p> 585running when nothing else is active.</p>
506<pre> struct dv_signal exitsig; 586<pre> struct ev_signal exitsig;
507 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 587 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
508 ev_signal_start (myloop, &amp;exitsig); 588 ev_signal_start (loop, &amp;exitsig);
509 evf_unref (myloop); 589 evf_unref (loop);
510 590
511</pre> 591</pre>
512 <p>Example: for some weird reason, unregister the above signal handler again.</p> 592 <p>Example: For some weird reason, unregister the above signal handler again.</p>
513<pre> ev_ref (myloop); 593<pre> ev_ref (loop);
514 ev_signal_stop (myloop, &amp;exitsig); 594 ev_signal_stop (loop, &amp;exitsig);
515 595
516</pre> 596</pre>
517 </dd> 597 </dd>
518</dl> 598</dl>
519 599
520 600
521 601
522 602
523 603
524</div> 604</div>
525<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 605<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
526<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 606<div id="ANATOMY_OF_A_WATCHER_CONTENT">
527<p>A watcher is a structure that you create and register to record your 607<p>A watcher is a structure that you create and register to record your
528interest in some event. For instance, if you want to wait for STDIN to 608interest in some event. For instance, if you want to wait for STDIN to
529become readable, you would create an <code>ev_io</code> watcher for that:</p> 609become readable, you would create an <code>ev_io</code> watcher for that:</p>
530<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 610<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
606received events. Callbacks of both watcher types can start and stop as 686received events. Callbacks of both watcher types can start and stop as
607many watchers as they want, and all of them will be taken into account 687many watchers as they want, and all of them will be taken into account
608(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 688(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
609<code>ev_loop</code> from blocking).</p> 689<code>ev_loop</code> from blocking).</p>
610 </dd> 690 </dd>
691 <dt><code>EV_EMBED</code></dt>
692 <dd>
693 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
694 </dd>
695 <dt><code>EV_FORK</code></dt>
696 <dd>
697 <p>The event loop has been resumed in the child process after fork (see
698<code>ev_fork</code>).</p>
699 </dd>
611 <dt><code>EV_ERROR</code></dt> 700 <dt><code>EV_ERROR</code></dt>
612 <dd> 701 <dd>
613 <p>An unspecified error has occured, the watcher has been stopped. This might 702 <p>An unspecified error has occured, the watcher has been stopped. This might
614happen because the watcher could not be properly started because libev 703happen because the watcher could not be properly started because libev
615ran out of memory, a file descriptor was found to be closed or any other 704ran out of memory, a file descriptor was found to be closed or any other
… …
681 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
682 <dd> 771 <dd>
683 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 772 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
684events but its callback has not yet been invoked). As long as a watcher 773events but its callback has not yet been invoked). As long as a watcher
685is pending (but not active) you must not call an init function on it (but 774is pending (but not active) you must not call an init function on it (but
686<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 775<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
687libev (e.g. you cnanot <code>free ()</code> it).</p> 776make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
777it).</p>
688 </dd> 778 </dd>
689 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
690 <dd> 780 <dd>
691 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
692 </dd> 782 </dd>
693 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
694 <dd> 784 <dd>
695 <p>Change the callback. You can change the callback at virtually any time 785 <p>Change the callback. You can change the callback at virtually any time
696(modulo threads).</p> 786(modulo threads).</p>
787 </dd>
788 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
789 <dt>int ev_priority (ev_TYPE *watcher)</dt>
790 <dd>
791 <p>Set and query the priority of the watcher. The priority is a small
792integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
793(default: <code>-2</code>). Pending watchers with higher priority will be invoked
794before watchers with lower priority, but priority will not keep watchers
795from being executed (except for <code>ev_idle</code> watchers).</p>
796 <p>This means that priorities are <i>only</i> used for ordering callback
797invocation after new events have been received. This is useful, for
798example, to reduce latency after idling, or more often, to bind two
799watchers on the same event and make sure one is called first.</p>
800 <p>If you need to suppress invocation when higher priority events are pending
801you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
802 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
803pending.</p>
804 <p>The default priority used by watchers when no priority has been set is
805always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
806 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
807fine, as long as you do not mind that the priority value you query might
808or might not have been adjusted to be within valid range.</p>
809 </dd>
810 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
811 <dd>
812 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
813<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
814can deal with that fact.</p>
815 </dd>
816 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
817 <dd>
818 <p>If the watcher is pending, this function returns clears its pending status
819and returns its <code>revents</code> bitset (as if its callback was invoked). If the
820watcher isn't pending it does nothing and returns <code>0</code>.</p>
697 </dd> 821 </dd>
698</dl> 822</dl>
699 823
700 824
701 825
… …
726 struct my_io *w = (struct my_io *)w_; 850 struct my_io *w = (struct my_io *)w_;
727 ... 851 ...
728 } 852 }
729 853
730</pre> 854</pre>
731<p>More interesting and less C-conformant ways of catsing your callback type 855<p>More interesting and less C-conformant ways of casting your callback type
732have been omitted....</p> 856instead have been omitted.</p>
857<p>Another common scenario is having some data structure with multiple
858watchers:</p>
859<pre> struct my_biggy
860 {
861 int some_data;
862 ev_timer t1;
863 ev_timer t2;
864 }
733 865
866</pre>
867<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
868you need to use <code>offsetof</code>:</p>
869<pre> #include &lt;stddef.h&gt;
734 870
871 static void
872 t1_cb (EV_P_ struct ev_timer *w, int revents)
873 {
874 struct my_biggy big = (struct my_biggy *
875 (((char *)w) - offsetof (struct my_biggy, t1));
876 }
735 877
878 static void
879 t2_cb (EV_P_ struct ev_timer *w, int revents)
880 {
881 struct my_biggy big = (struct my_biggy *
882 (((char *)w) - offsetof (struct my_biggy, t2));
883 }
736 884
737 885
886
887
888</pre>
889
738</div> 890</div>
739<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 891<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
740<div id="WATCHER_TYPES_CONTENT"> 892<div id="WATCHER_TYPES_CONTENT">
741<p>This section describes each watcher in detail, but will not repeat 893<p>This section describes each watcher in detail, but will not repeat
742information given in the last section. Any initialisation/set macros, 894information given in the last section. Any initialisation/set macros,
743functions and members specific to the watcher type are explained.</p> 895functions and members specific to the watcher type are explained.</p>
744<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 896<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
784this situation even with a relatively standard program structure. Thus 936this situation even with a relatively standard program structure. Thus
785it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 937it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
786<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 938<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
787<p>If you cannot run the fd in non-blocking mode (for example you should not 939<p>If you cannot run the fd in non-blocking mode (for example you should not
788play around with an Xlib connection), then you have to seperately re-test 940play around with an Xlib connection), then you have to seperately re-test
789wether a file descriptor is really ready with a known-to-be good interface 941whether a file descriptor is really ready with a known-to-be good interface
790such as poll (fortunately in our Xlib example, Xlib already does this on 942such as poll (fortunately in our Xlib example, Xlib already does this on
791its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
792<dl> 944<dl>
793 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 945 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
794 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
804 <dt>int events [read-only]</dt> 956 <dt>int events [read-only]</dt>
805 <dd> 957 <dd>
806 <p>The events being watched.</p> 958 <p>The events being watched.</p>
807 </dd> 959 </dd>
808</dl> 960</dl>
809<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 961<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
810readable, but only once. Since it is likely line-buffered, you could 962readable, but only once. Since it is likely line-buffered, you could
811attempt to read a whole line in the callback:</p> 963attempt to read a whole line in the callback.</p>
812<pre> static void 964<pre> static void
813 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 965 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
814 { 966 {
815 ev_io_stop (loop, w); 967 ev_io_stop (loop, w);
816 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 968 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
865 </dd> 1017 </dd>
866 <dt>ev_timer_again (loop)</dt> 1018 <dt>ev_timer_again (loop)</dt>
867 <dd> 1019 <dd>
868 <p>This will act as if the timer timed out and restart it again if it is 1020 <p>This will act as if the timer timed out and restart it again if it is
869repeating. The exact semantics are:</p> 1021repeating. The exact semantics are:</p>
1022 <p>If the timer is pending, its pending status is cleared.</p>
870 <p>If the timer is started but nonrepeating, stop it.</p> 1023 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
871 <p>If the timer is repeating, either start it if necessary (with the repeat 1024 <p>If the timer is repeating, either start it if necessary (with the
872value), or reset the running timer to the repeat value.</p> 1025<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
873 <p>This sounds a bit complicated, but here is a useful and typical 1026 <p>This sounds a bit complicated, but here is a useful and typical
874example: Imagine you have a tcp connection and you want a so-called 1027example: Imagine you have a tcp connection and you want a so-called idle
875idle timeout, that is, you want to be called when there have been, 1028timeout, that is, you want to be called when there have been, say, 60
876say, 60 seconds of inactivity on the socket. The easiest way to do 1029seconds of inactivity on the socket. The easiest way to do this is to
877this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 1030configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
878<code>ev_timer_again</code> each time you successfully read or write some data. If 1031<code>ev_timer_again</code> each time you successfully read or write some data. If
879you go into an idle state where you do not expect data to travel on the 1032you go into an idle state where you do not expect data to travel on the
880socket, you can stop the timer, and again will automatically restart it if 1033socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
881need be.</p> 1034automatically restart it if need be.</p>
882 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1035 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
883and only ever use the <code>repeat</code> value:</p> 1036altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
884<pre> ev_timer_init (timer, callback, 0., 5.); 1037<pre> ev_timer_init (timer, callback, 0., 5.);
885 ev_timer_again (loop, timer); 1038 ev_timer_again (loop, timer);
886 ... 1039 ...
887 timer-&gt;again = 17.; 1040 timer-&gt;again = 17.;
888 ev_timer_again (loop, timer); 1041 ev_timer_again (loop, timer);
889 ... 1042 ...
890 timer-&gt;again = 10.; 1043 timer-&gt;again = 10.;
891 ev_timer_again (loop, timer); 1044 ev_timer_again (loop, timer);
892 1045
893</pre> 1046</pre>
894 <p>This is more efficient then stopping/starting the timer eahc time you want 1047 <p>This is more slightly efficient then stopping/starting the timer each time
895to modify its timeout value.</p> 1048you want to modify its timeout value.</p>
896 </dd> 1049 </dd>
897 <dt>ev_tstamp repeat [read-write]</dt> 1050 <dt>ev_tstamp repeat [read-write]</dt>
898 <dd> 1051 <dd>
899 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1052 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
900or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1053or <code>ev_timer_again</code> is called and determines the next timeout (if any),
901which is also when any modifications are taken into account.</p> 1054which is also when any modifications are taken into account.</p>
902 </dd> 1055 </dd>
903</dl> 1056</dl>
904<p>Example: create a timer that fires after 60 seconds.</p> 1057<p>Example: Create a timer that fires after 60 seconds.</p>
905<pre> static void 1058<pre> static void
906 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1059 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
907 { 1060 {
908 .. one minute over, w is actually stopped right here 1061 .. one minute over, w is actually stopped right here
909 } 1062 }
… …
911 struct ev_timer mytimer; 1064 struct ev_timer mytimer;
912 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1065 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
913 ev_timer_start (loop, &amp;mytimer); 1066 ev_timer_start (loop, &amp;mytimer);
914 1067
915</pre> 1068</pre>
916<p>Example: create a timeout timer that times out after 10 seconds of 1069<p>Example: Create a timeout timer that times out after 10 seconds of
917inactivity.</p> 1070inactivity.</p>
918<pre> static void 1071<pre> static void
919 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1072 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
920 { 1073 {
921 .. ten seconds without any activity 1074 .. ten seconds without any activity
… …
944but on wallclock time (absolute time). You can tell a periodic watcher 1097but on wallclock time (absolute time). You can tell a periodic watcher
945to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1098to trigger &quot;at&quot; some specific point in time. For example, if you tell a
946periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1099periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
947+ 10.</code>) and then reset your system clock to the last year, then it will 1100+ 10.</code>) and then reset your system clock to the last year, then it will
948take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1101take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
949roughly 10 seconds later and of course not if you reset your system time 1102roughly 10 seconds later).</p>
950again).</p>
951<p>They can also be used to implement vastly more complex timers, such as 1103<p>They can also be used to implement vastly more complex timers, such as
952triggering an event on eahc midnight, local time.</p> 1104triggering an event on each midnight, local time or other, complicated,
1105rules.</p>
953<p>As with timers, the callback is guarenteed to be invoked only when the 1106<p>As with timers, the callback is guarenteed to be invoked only when the
954time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1107time (<code>at</code>) has been passed, but if multiple periodic timers become ready
955during the same loop iteration then order of execution is undefined.</p> 1108during the same loop iteration then order of execution is undefined.</p>
956<dl> 1109<dl>
957 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1110 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
959 <dd> 1112 <dd>
960 <p>Lots of arguments, lets sort it out... There are basically three modes of 1113 <p>Lots of arguments, lets sort it out... There are basically three modes of
961operation, and we will explain them from simplest to complex:</p> 1114operation, and we will explain them from simplest to complex:</p>
962 <p> 1115 <p>
963 <dl> 1116 <dl>
964 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1117 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
965 <dd> 1118 <dd>
966 <p>In this configuration the watcher triggers an event at the wallclock time 1119 <p>In this configuration the watcher triggers an event at the wallclock time
967<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1120<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
968that is, if it is to be run at January 1st 2011 then it will run when the 1121that is, if it is to be run at January 1st 2011 then it will run when the
969system time reaches or surpasses this time.</p> 1122system time reaches or surpasses this time.</p>
970 </dd> 1123 </dd>
971 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1124 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
972 <dd> 1125 <dd>
973 <p>In this mode the watcher will always be scheduled to time out at the next 1126 <p>In this mode the watcher will always be scheduled to time out at the next
974<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1127<code>at + N * interval</code> time (for some integer N, which can also be negative)
975of any time jumps.</p> 1128and then repeat, regardless of any time jumps.</p>
976 <p>This can be used to create timers that do not drift with respect to system 1129 <p>This can be used to create timers that do not drift with respect to system
977time:</p> 1130time:</p>
978<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
979 1132
980</pre> 1133</pre>
… …
983full hour (UTC), or more correctly, when the system time is evenly divisible 1136full hour (UTC), or more correctly, when the system time is evenly divisible
984by 3600.</p> 1137by 3600.</p>
985 <p>Another way to think about it (for the mathematically inclined) is that 1138 <p>Another way to think about it (for the mathematically inclined) is that
986<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1139<code>ev_periodic</code> will try to run the callback in this mode at the next possible
987time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1140time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1141 <p>For numerical stability it is preferable that the <code>at</code> value is near
1142<code>ev_now ()</code> (the current time), but there is no range requirement for
1143this value.</p>
988 </dd> 1144 </dd>
989 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1145 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
990 <dd> 1146 <dd>
991 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1147 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
992ignored. Instead, each time the periodic watcher gets scheduled, the 1148ignored. Instead, each time the periodic watcher gets scheduled, the
993reschedule callback will be called with the watcher as first, and the 1149reschedule callback will be called with the watcher as first, and the
994current time as second argument.</p> 1150current time as second argument.</p>
995 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1151 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
996ever, or make any event loop modifications</i>. If you need to stop it, 1152ever, or make any event loop modifications</i>. If you need to stop it,
997return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1153return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
998starting a prepare watcher).</p> 1154starting an <code>ev_prepare</code> watcher, which is legal).</p>
999 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1155 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1000ev_tstamp now)</code>, e.g.:</p> 1156ev_tstamp now)</code>, e.g.:</p>
1001<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1157<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1002 { 1158 {
1003 return now + 60.; 1159 return now + 60.;
… …
1024 <p>Simply stops and restarts the periodic watcher again. This is only useful 1180 <p>Simply stops and restarts the periodic watcher again. This is only useful
1025when you changed some parameters or the reschedule callback would return 1181when you changed some parameters or the reschedule callback would return
1026a different time than the last time it was called (e.g. in a crond like 1182a different time than the last time it was called (e.g. in a crond like
1027program when the crontabs have changed).</p> 1183program when the crontabs have changed).</p>
1028 </dd> 1184 </dd>
1185 <dt>ev_tstamp offset [read-write]</dt>
1186 <dd>
1187 <p>When repeating, this contains the offset value, otherwise this is the
1188absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1189 <p>Can be modified any time, but changes only take effect when the periodic
1190timer fires or <code>ev_periodic_again</code> is being called.</p>
1191 </dd>
1029 <dt>ev_tstamp interval [read-write]</dt> 1192 <dt>ev_tstamp interval [read-write]</dt>
1030 <dd> 1193 <dd>
1031 <p>The current interval value. Can be modified any time, but changes only 1194 <p>The current interval value. Can be modified any time, but changes only
1032take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1195take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1033called.</p> 1196called.</p>
… …
1037 <p>The current reschedule callback, or <code>0</code>, if this functionality is 1200 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1038switched off. Can be changed any time, but changes only take effect when 1201switched off. Can be changed any time, but changes only take effect when
1039the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> 1202the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1040 </dd> 1203 </dd>
1041</dl> 1204</dl>
1042<p>Example: call a callback every hour, or, more precisely, whenever the 1205<p>Example: Call a callback every hour, or, more precisely, whenever the
1043system clock is divisible by 3600. The callback invocation times have 1206system clock is divisible by 3600. The callback invocation times have
1044potentially a lot of jittering, but good long-term stability.</p> 1207potentially a lot of jittering, but good long-term stability.</p>
1045<pre> static void 1208<pre> static void
1046 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1209 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1047 { 1210 {
… …
1051 struct ev_periodic hourly_tick; 1214 struct ev_periodic hourly_tick;
1052 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1215 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1053 ev_periodic_start (loop, &amp;hourly_tick); 1216 ev_periodic_start (loop, &amp;hourly_tick);
1054 1217
1055</pre> 1218</pre>
1056<p>Example: the same as above, but use a reschedule callback to do it:</p> 1219<p>Example: The same as above, but use a reschedule callback to do it:</p>
1057<pre> #include &lt;math.h&gt; 1220<pre> #include &lt;math.h&gt;
1058 1221
1059 static ev_tstamp 1222 static ev_tstamp
1060 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1223 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1061 { 1224 {
… …
1063 } 1226 }
1064 1227
1065 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1228 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1066 1229
1067</pre> 1230</pre>
1068<p>Example: call a callback every hour, starting now:</p> 1231<p>Example: Call a callback every hour, starting now:</p>
1069<pre> struct ev_periodic hourly_tick; 1232<pre> struct ev_periodic hourly_tick;
1070 ev_periodic_init (&amp;hourly_tick, clock_cb, 1233 ev_periodic_init (&amp;hourly_tick, clock_cb,
1071 fmod (ev_now (loop), 3600.), 3600., 0); 1234 fmod (ev_now (loop), 3600.), 3600., 0);
1072 ev_periodic_start (loop, &amp;hourly_tick); 1235 ev_periodic_start (loop, &amp;hourly_tick);
1073 1236
… …
1134 <dd> 1297 <dd>
1135 <p>The process exit/trace status caused by <code>rpid</code> (see your systems 1298 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1136<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> 1299<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1137 </dd> 1300 </dd>
1138</dl> 1301</dl>
1139<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1302<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1140<pre> static void 1303<pre> static void
1141 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1304 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1142 { 1305 {
1143 ev_unloop (loop, EVUNLOOP_ALL); 1306 ev_unloop (loop, EVUNLOOP_ALL);
1144 } 1307 }
… …
1161<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1324<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1162not exist&quot; is a status change like any other. The condition &quot;path does 1325not exist&quot; is a status change like any other. The condition &quot;path does
1163not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1326not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1164otherwise always forced to be at least one) and all the other fields of 1327otherwise always forced to be at least one) and all the other fields of
1165the stat buffer having unspecified contents.</p> 1328the stat buffer having unspecified contents.</p>
1329<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1330relative and your working directory changes, the behaviour is undefined.</p>
1166<p>Since there is no standard to do this, the portable implementation simply 1331<p>Since there is no standard to do this, the portable implementation simply
1167calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You 1332calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1168can specify a recommended polling interval for this case. If you specify 1333can specify a recommended polling interval for this case. If you specify
1169a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1334a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1170unspecified default</i> value will be used (which you can expect to be around 1335unspecified default</i> value will be used (which you can expect to be around
1171five seconds, although this might change dynamically). Libev will also 1336five seconds, although this might change dynamically). Libev will also
1172impose a minimum interval which is currently around <code>0.1</code>, but thats 1337impose a minimum interval which is currently around <code>0.1</code>, but thats
1173usually overkill.</p> 1338usually overkill.</p>
1174<p>This watcher type is not meant for massive numbers of stat watchers, 1339<p>This watcher type is not meant for massive numbers of stat watchers,
1175as even with OS-supported change notifications, this can be 1340as even with OS-supported change notifications, this can be
1176resource-intensive.</p> 1341resource-intensive.</p>
1177<p>At the time of this writing, no specific OS backends are implemented, but 1342<p>At the time of this writing, only the Linux inotify interface is
1178if demand increases, at least a kqueue and inotify backend will be added.</p> 1343implemented (implementing kqueue support is left as an exercise for the
1344reader). Inotify will be used to give hints only and should not change the
1345semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1346to fall back to regular polling again even with inotify, but changes are
1347usually detected immediately, and if the file exists there will be no
1348polling.</p>
1179<dl> 1349<dl>
1180 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1350 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1181 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1351 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1182 <dd> 1352 <dd>
1183 <p>Configures the watcher to wait for status changes of the given 1353 <p>Configures the watcher to wait for status changes of the given
… …
1246</pre> 1416</pre>
1247 1417
1248</div> 1418</div>
1249<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1419<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1250<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1420<div id="code_ev_idle_code_when_you_ve_got_no-2">
1251<p>Idle watchers trigger events when there are no other events are pending 1421<p>Idle watchers trigger events when no other events of the same or higher
1252(prepare, check and other idle watchers do not count). That is, as long 1422priority are pending (prepare, check and other idle watchers do not
1253as your process is busy handling sockets or timeouts (or even signals, 1423count).</p>
1254imagine) it will not be triggered. But when your process is idle all idle 1424<p>That is, as long as your process is busy handling sockets or timeouts
1255watchers are being called again and again, once per event loop iteration - 1425(or even signals, imagine) of the same or higher priority it will not be
1426triggered. But when your process is idle (or only lower-priority watchers
1427are pending), the idle watchers are being called once per event loop
1256until stopped, that is, or your process receives more events and becomes 1428iteration - until stopped, that is, or your process receives more events
1257busy.</p> 1429and becomes busy again with higher priority stuff.</p>
1258<p>The most noteworthy effect is that as long as any idle watchers are 1430<p>The most noteworthy effect is that as long as any idle watchers are
1259active, the process will not block when waiting for new events.</p> 1431active, the process will not block when waiting for new events.</p>
1260<p>Apart from keeping your process non-blocking (which is a useful 1432<p>Apart from keeping your process non-blocking (which is a useful
1261effect on its own sometimes), idle watchers are a good place to do 1433effect on its own sometimes), idle watchers are a good place to do
1262&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1434&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1267 <p>Initialises and configures the idle watcher - it has no parameters of any 1439 <p>Initialises and configures the idle watcher - it has no parameters of any
1268kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1440kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1269believe me.</p> 1441believe me.</p>
1270 </dd> 1442 </dd>
1271</dl> 1443</dl>
1272<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1444<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1273callback, free it. Alos, use no error checking, as usual.</p> 1445callback, free it. Also, use no error checking, as usual.</p>
1274<pre> static void 1446<pre> static void
1275 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1447 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1276 { 1448 {
1277 free (w); 1449 free (w);
1278 // now do something you wanted to do when the program has 1450 // now do something you wanted to do when the program has
… …
1322are ready to run (it's actually more complicated: it only runs coroutines 1494are ready to run (it's actually more complicated: it only runs coroutines
1323with priority higher than or equal to the event loop and one coroutine 1495with priority higher than or equal to the event loop and one coroutine
1324of lower priority, but only once, using idle watchers to keep the event 1496of lower priority, but only once, using idle watchers to keep the event
1325loop from blocking if lower-priority coroutines are active, thus mapping 1497loop from blocking if lower-priority coroutines are active, thus mapping
1326low-priority coroutines to idle/background tasks).</p> 1498low-priority coroutines to idle/background tasks).</p>
1499<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1500priority, to ensure that they are being run before any other watchers
1501after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1502too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1503supports this, they will be called before other <code>ev_check</code> watchers did
1504their job. As <code>ev_check</code> watchers are often used to embed other event
1505loops those other event loops might be in an unusable state until their
1506<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1507others).</p>
1327<dl> 1508<dl>
1328 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1509 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1329 <dt>ev_check_init (ev_check *, callback)</dt> 1510 <dt>ev_check_init (ev_check *, callback)</dt>
1330 <dd> 1511 <dd>
1331 <p>Initialises and configures the prepare or check watcher - they have no 1512 <p>Initialises and configures the prepare or check watcher - they have no
1332parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1513parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1333macros, but using them is utterly, utterly and completely pointless.</p> 1514macros, but using them is utterly, utterly and completely pointless.</p>
1334 </dd> 1515 </dd>
1335</dl> 1516</dl>
1336<p>Example: To include a library such as adns, you would add IO watchers 1517<p>There are a number of principal ways to embed other event loops or modules
1337and a timeout watcher in a prepare handler, as required by libadns, and 1518into libev. Here are some ideas on how to include libadns into libev
1519(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1520use for an actually working example. Another Perl module named <code>EV::Glib</code>
1521embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1522into the Glib event loop).</p>
1523<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1338in a check watcher, destroy them and call into libadns. What follows is 1524and in a check watcher, destroy them and call into libadns. What follows
1339pseudo-code only of course:</p> 1525is pseudo-code only of course. This requires you to either use a low
1526priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1527the callbacks for the IO/timeout watchers might not have been called yet.</p>
1340<pre> static ev_io iow [nfd]; 1528<pre> static ev_io iow [nfd];
1341 static ev_timer tw; 1529 static ev_timer tw;
1342 1530
1343 static void 1531 static void
1344 io_cb (ev_loop *loop, ev_io *w, int revents) 1532 io_cb (ev_loop *loop, ev_io *w, int revents)
1345 { 1533 {
1346 // set the relevant poll flags
1347 // could also call adns_processreadable etc. here
1348 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1349 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1350 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1351 } 1534 }
1352 1535
1353 // create io watchers for each fd and a timer before blocking 1536 // create io watchers for each fd and a timer before blocking
1354 static void 1537 static void
1355 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1538 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1356 { 1539 {
1357 int timeout = 3600000;truct pollfd fds [nfd]; 1540 int timeout = 3600000;
1541 struct pollfd fds [nfd];
1358 // actual code will need to loop here and realloc etc. 1542 // actual code will need to loop here and realloc etc.
1359 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1543 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1360 1544
1361 /* the callback is illegal, but won't be called as we stop during check */ 1545 /* the callback is illegal, but won't be called as we stop during check */
1362 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1546 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1363 ev_timer_start (loop, &amp;tw); 1547 ev_timer_start (loop, &amp;tw);
1364 1548
1365 // create on ev_io per pollfd 1549 // create one ev_io per pollfd
1366 for (int i = 0; i &lt; nfd; ++i) 1550 for (int i = 0; i &lt; nfd; ++i)
1367 { 1551 {
1368 ev_io_init (iow + i, io_cb, fds [i].fd, 1552 ev_io_init (iow + i, io_cb, fds [i].fd,
1369 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1553 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1370 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1554 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1371 1555
1372 fds [i].revents = 0; 1556 fds [i].revents = 0;
1373 iow [i].data = fds + i;
1374 ev_io_start (loop, iow + i); 1557 ev_io_start (loop, iow + i);
1375 } 1558 }
1376 } 1559 }
1377 1560
1378 // stop all watchers after blocking 1561 // stop all watchers after blocking
… …
1380 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1563 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1381 { 1564 {
1382 ev_timer_stop (loop, &amp;tw); 1565 ev_timer_stop (loop, &amp;tw);
1383 1566
1384 for (int i = 0; i &lt; nfd; ++i) 1567 for (int i = 0; i &lt; nfd; ++i)
1568 {
1569 // set the relevant poll flags
1570 // could also call adns_processreadable etc. here
1571 struct pollfd *fd = fds + i;
1572 int revents = ev_clear_pending (iow + i);
1573 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1574 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1575
1576 // now stop the watcher
1385 ev_io_stop (loop, iow + i); 1577 ev_io_stop (loop, iow + i);
1578 }
1386 1579
1387 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1580 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1581 }
1582
1583</pre>
1584<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1585in the prepare watcher and would dispose of the check watcher.</p>
1586<p>Method 3: If the module to be embedded supports explicit event
1587notification (adns does), you can also make use of the actual watcher
1588callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1589<pre> static void
1590 timer_cb (EV_P_ ev_timer *w, int revents)
1591 {
1592 adns_state ads = (adns_state)w-&gt;data;
1593 update_now (EV_A);
1594
1595 adns_processtimeouts (ads, &amp;tv_now);
1596 }
1597
1598 static void
1599 io_cb (EV_P_ ev_io *w, int revents)
1600 {
1601 adns_state ads = (adns_state)w-&gt;data;
1602 update_now (EV_A);
1603
1604 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1605 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1606 }
1607
1608 // do not ever call adns_afterpoll
1609
1610</pre>
1611<p>Method 4: Do not use a prepare or check watcher because the module you
1612want to embed is too inflexible to support it. Instead, youc na override
1613their poll function. The drawback with this solution is that the main
1614loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1615this.</p>
1616<pre> static gint
1617 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1618 {
1619 int got_events = 0;
1620
1621 for (n = 0; n &lt; nfds; ++n)
1622 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1623
1624 if (timeout &gt;= 0)
1625 // create/start timer
1626
1627 // poll
1628 ev_loop (EV_A_ 0);
1629
1630 // stop timer again
1631 if (timeout &gt;= 0)
1632 ev_timer_stop (EV_A_ &amp;to);
1633
1634 // stop io watchers again - their callbacks should have set
1635 for (n = 0; n &lt; nfds; ++n)
1636 ev_io_stop (EV_A_ iow [n]);
1637
1638 return got_events;
1388 } 1639 }
1389 1640
1390 1641
1391 1642
1392 1643
… …
1480 1731
1481 1732
1482 1733
1483 1734
1484</div> 1735</div>
1485<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1736<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1737<div id="code_ev_fork_code_the_audacity_to_re-2">
1738<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1739whoever is a good citizen cared to tell libev about it by calling
1740<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1741event loop blocks next and before <code>ev_check</code> watchers are being called,
1742and only in the child after the fork. If whoever good citizen calling
1743<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1744handlers will be invoked, too, of course.</p>
1745<dl>
1746 <dt>ev_fork_init (ev_signal *, callback)</dt>
1747 <dd>
1748 <p>Initialises and configures the fork watcher - it has no parameters of any
1749kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1750believe me.</p>
1751 </dd>
1752</dl>
1753
1754
1755
1756
1757
1758</div>
1759<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1486<div id="OTHER_FUNCTIONS_CONTENT"> 1760<div id="OTHER_FUNCTIONS_CONTENT">
1487<p>There are some other functions of possible interest. Described. Here. Now.</p> 1761<p>There are some other functions of possible interest. Described. Here. Now.</p>
1488<dl> 1762<dl>
1489 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1763 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1490 <dd> 1764 <dd>
… …
1537 1811
1538 1812
1539 1813
1540 1814
1541</div> 1815</div>
1542<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1816<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1543<div id="LIBEVENT_EMULATION_CONTENT"> 1817<div id="LIBEVENT_EMULATION_CONTENT">
1544<p>Libev offers a compatibility emulation layer for libevent. It cannot 1818<p>Libev offers a compatibility emulation layer for libevent. It cannot
1545emulate the internals of libevent, so here are some usage hints:</p> 1819emulate the internals of libevent, so here are some usage hints:</p>
1546<dl> 1820<dl>
1547 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1821 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1557 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1831 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1558to use the libev header file and library.</dt> 1832to use the libev header file and library.</dt>
1559</dl> 1833</dl>
1560 1834
1561</div> 1835</div>
1562<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1836<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1563<div id="C_SUPPORT_CONTENT"> 1837<div id="C_SUPPORT_CONTENT">
1564<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1838<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1565you to use some convinience methods to start/stop watchers and also change 1839you to use some convinience methods to start/stop watchers and also change
1566the callback model to a model using method callbacks on objects.</p> 1840the callback model to a model using method callbacks on objects.</p>
1567<p>To use it,</p> 1841<p>To use it,</p>
1568<pre> #include &lt;ev++.h&gt; 1842<pre> #include &lt;ev++.h&gt;
1569 1843
1570</pre> 1844</pre>
1571<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1845<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1572and puts all of its definitions (many of them macros) into the global 1846of them macros) into the global namespace. All C++ specific things are
1573namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1847put into the <code>ev</code> namespace. It should support all the same embedding
1574<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1848options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1575<code>EV_MULTIPLICITY</code>.</p> 1849<p>Care has been taken to keep the overhead low. The only data member the C++
1850classes add (compared to plain C-style watchers) is the event loop pointer
1851that the watcher is associated with (or no additional members at all if
1852you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1853<p>Currently, functions, and static and non-static member functions can be
1854used as callbacks. Other types should be easy to add as long as they only
1855need one additional pointer for context. If you need support for other
1856types of functors please contact the author (preferably after implementing
1857it).</p>
1576<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1858<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1577<dl> 1859<dl>
1578 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1860 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1579 <dd> 1861 <dd>
1580 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1862 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1591which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1873which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1592defines by many implementations.</p> 1874defines by many implementations.</p>
1593 <p>All of those classes have these methods:</p> 1875 <p>All of those classes have these methods:</p>
1594 <p> 1876 <p>
1595 <dl> 1877 <dl>
1596 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1878 <dt>ev::TYPE::TYPE ()</dt>
1597 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1879 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1598 <dt>ev::TYPE::~TYPE</dt> 1880 <dt>ev::TYPE::~TYPE</dt>
1599 <dd> 1881 <dd>
1600 <p>The constructor takes a pointer to an object and a method pointer to 1882 <p>The constructor (optionally) takes an event loop to associate the watcher
1601the event handler callback to call in this class. The constructor calls 1883with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1602<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1884 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1603before starting it. If you do not specify a loop then the constructor 1885<code>set</code> method before starting it.</p>
1604automatically associates the default loop with this watcher.</p> 1886 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1887method to set a callback before you can start the watcher.</p>
1888 <p>(The reason why you have to use a method is a limitation in C++ which does
1889not allow explicit template arguments for constructors).</p>
1605 <p>The destructor automatically stops the watcher if it is active.</p> 1890 <p>The destructor automatically stops the watcher if it is active.</p>
1891 </dd>
1892 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1893 <dd>
1894 <p>This method sets the callback method to call. The method has to have a
1895signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1896first argument and the <code>revents</code> as second. The object must be given as
1897parameter and is stored in the <code>data</code> member of the watcher.</p>
1898 <p>This method synthesizes efficient thunking code to call your method from
1899the C callback that libev requires. If your compiler can inline your
1900callback (i.e. it is visible to it at the place of the <code>set</code> call and
1901your compiler is good :), then the method will be fully inlined into the
1902thunking function, making it as fast as a direct C callback.</p>
1903 <p>Example: simple class declaration and watcher initialisation</p>
1904<pre> struct myclass
1905 {
1906 void io_cb (ev::io &amp;w, int revents) { }
1907 }
1908
1909 myclass obj;
1910 ev::io iow;
1911 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1912
1913</pre>
1914 </dd>
1915 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1916 <dd>
1917 <p>Also sets a callback, but uses a static method or plain function as
1918callback. The optional <code>data</code> argument will be stored in the watcher's
1919<code>data</code> member and is free for you to use.</p>
1920 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1921 <p>See the method-<code>set</code> above for more details.</p>
1922 <p>Example:</p>
1923<pre> static void io_cb (ev::io &amp;w, int revents) { }
1924 iow.set &lt;io_cb&gt; ();
1925
1926</pre>
1606 </dd> 1927 </dd>
1607 <dt>w-&gt;set (struct ev_loop *)</dt> 1928 <dt>w-&gt;set (struct ev_loop *)</dt>
1608 <dd> 1929 <dd>
1609 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1930 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1610do this when the watcher is inactive (and not pending either).</p> 1931do this when the watcher is inactive (and not pending either).</p>
1611 </dd> 1932 </dd>
1612 <dt>w-&gt;set ([args])</dt> 1933 <dt>w-&gt;set ([args])</dt>
1613 <dd> 1934 <dd>
1614 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1935 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1615called at least once. Unlike the C counterpart, an active watcher gets 1936called at least once. Unlike the C counterpart, an active watcher gets
1616automatically stopped and restarted.</p> 1937automatically stopped and restarted when reconfiguring it with this
1938method.</p>
1617 </dd> 1939 </dd>
1618 <dt>w-&gt;start ()</dt> 1940 <dt>w-&gt;start ()</dt>
1619 <dd> 1941 <dd>
1620 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1942 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1621constructor already takes the loop.</p> 1943constructor already stores the event loop.</p>
1622 </dd> 1944 </dd>
1623 <dt>w-&gt;stop ()</dt> 1945 <dt>w-&gt;stop ()</dt>
1624 <dd> 1946 <dd>
1625 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1947 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1626 </dd> 1948 </dd>
… …
1630<code>ev_TYPE_again</code> function.</p> 1952<code>ev_TYPE_again</code> function.</p>
1631 </dd> 1953 </dd>
1632 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1954 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1633 <dd> 1955 <dd>
1634 <p>Invokes <code>ev_embed_sweep</code>.</p> 1956 <p>Invokes <code>ev_embed_sweep</code>.</p>
1957 </dd>
1958 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1959 <dd>
1960 <p>Invokes <code>ev_stat_stat</code>.</p>
1635 </dd> 1961 </dd>
1636 </dl> 1962 </dl>
1637 </p> 1963 </p>
1638 </dd> 1964 </dd>
1639</dl> 1965</dl>
… …
1646 1972
1647 myclass (); 1973 myclass ();
1648 } 1974 }
1649 1975
1650 myclass::myclass (int fd) 1976 myclass::myclass (int fd)
1651 : io (this, &amp;myclass::io_cb),
1652 idle (this, &amp;myclass::idle_cb)
1653 { 1977 {
1978 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1979 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1980
1654 io.start (fd, ev::READ); 1981 io.start (fd, ev::READ);
1655 } 1982 }
1656 1983
1657</pre>
1658 1984
1985
1986
1987</pre>
1988
1659</div> 1989</div>
1660<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1990<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1991<div id="MACRO_MAGIC_CONTENT">
1992<p>Libev can be compiled with a variety of options, the most fundemantal is
1993<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1994callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1995<p>To make it easier to write programs that cope with either variant, the
1996following macros are defined:</p>
1997<dl>
1998 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1999 <dd>
2000 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
2001loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
2002<code>EV_A_</code> is used when other arguments are following. Example:</p>
2003<pre> ev_unref (EV_A);
2004 ev_timer_add (EV_A_ watcher);
2005 ev_loop (EV_A_ 0);
2006
2007</pre>
2008 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
2009which is often provided by the following macro.</p>
2010 </dd>
2011 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
2012 <dd>
2013 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
2014loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
2015<code>EV_P_</code> is used when other parameters are following. Example:</p>
2016<pre> // this is how ev_unref is being declared
2017 static void ev_unref (EV_P);
2018
2019 // this is how you can declare your typical callback
2020 static void cb (EV_P_ ev_timer *w, int revents)
2021
2022</pre>
2023 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
2024suitable for use with <code>EV_A</code>.</p>
2025 </dd>
2026 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
2027 <dd>
2028 <p>Similar to the other two macros, this gives you the value of the default
2029loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
2030 </dd>
2031</dl>
2032<p>Example: Declare and initialise a check watcher, utilising the above
2033macros so it will work regardless of whether multiple loops are supported
2034or not.</p>
2035<pre> static void
2036 check_cb (EV_P_ ev_timer *w, int revents)
2037 {
2038 ev_check_stop (EV_A_ w);
2039 }
2040
2041 ev_check check;
2042 ev_check_init (&amp;check, check_cb);
2043 ev_check_start (EV_DEFAULT_ &amp;check);
2044 ev_loop (EV_DEFAULT_ 0);
2045
2046</pre>
2047
2048</div>
2049<h1 id="EMBEDDING">EMBEDDING</h1>
1661<div id="EMBEDDING_CONTENT"> 2050<div id="EMBEDDING_CONTENT">
1662<p>Libev can (and often is) directly embedded into host 2051<p>Libev can (and often is) directly embedded into host
1663applications. Examples of applications that embed it include the Deliantra 2052applications. Examples of applications that embed it include the Deliantra
1664Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2053Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1665and rxvt-unicode.</p> 2054and rxvt-unicode.</p>
… …
1702 ev_vars.h 2091 ev_vars.h
1703 ev_wrap.h 2092 ev_wrap.h
1704 2093
1705 ev_win32.c required on win32 platforms only 2094 ev_win32.c required on win32 platforms only
1706 2095
1707 ev_select.c only when select backend is enabled (which is by default) 2096 ev_select.c only when select backend is enabled (which is enabled by default)
1708 ev_poll.c only when poll backend is enabled (disabled by default) 2097 ev_poll.c only when poll backend is enabled (disabled by default)
1709 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2098 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1710 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2099 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1711 ev_port.c only when the solaris port backend is enabled (disabled by default) 2100 ev_port.c only when the solaris port backend is enabled (disabled by default)
1712 2101
… …
1839 </dd> 2228 </dd>
1840 <dt>EV_USE_DEVPOLL</dt> 2229 <dt>EV_USE_DEVPOLL</dt>
1841 <dd> 2230 <dd>
1842 <p>reserved for future expansion, works like the USE symbols above.</p> 2231 <p>reserved for future expansion, works like the USE symbols above.</p>
1843 </dd> 2232 </dd>
2233 <dt>EV_USE_INOTIFY</dt>
2234 <dd>
2235 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2236interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2237be detected at runtime.</p>
2238 </dd>
1844 <dt>EV_H</dt> 2239 <dt>EV_H</dt>
1845 <dd> 2240 <dd>
1846 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2241 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1847undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2242undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1848can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2243can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1871will have the <code>struct ev_loop *</code> as first argument, and you can create 2266will have the <code>struct ev_loop *</code> as first argument, and you can create
1872additional independent event loops. Otherwise there will be no support 2267additional independent event loops. Otherwise there will be no support
1873for multiple event loops and there is no first event loop pointer 2268for multiple event loops and there is no first event loop pointer
1874argument. Instead, all functions act on the single default loop.</p> 2269argument. Instead, all functions act on the single default loop.</p>
1875 </dd> 2270 </dd>
2271 <dt>EV_MINPRI</dt>
2272 <dt>EV_MAXPRI</dt>
2273 <dd>
2274 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2275<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2276provide for more priorities by overriding those symbols (usually defined
2277to be <code>-2</code> and <code>2</code>, respectively).</p>
2278 <p>When doing priority-based operations, libev usually has to linearly search
2279all the priorities, so having many of them (hundreds) uses a lot of space
2280and time, so using the defaults of five priorities (-2 .. +2) is usually
2281fine.</p>
2282 <p>If your embedding app does not need any priorities, defining these both to
2283<code>0</code> will save some memory and cpu.</p>
2284 </dd>
1876 <dt>EV_PERIODIC_ENABLE</dt> 2285 <dt>EV_PERIODIC_ENABLE</dt>
1877 <dd> 2286 <dd>
1878 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2287 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1879defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2288defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
1880code.</p> 2289code.</p>
1881 </dd> 2290 </dd>
2291 <dt>EV_IDLE_ENABLE</dt>
2292 <dd>
2293 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2294defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2295code.</p>
2296 </dd>
1882 <dt>EV_EMBED_ENABLE</dt> 2297 <dt>EV_EMBED_ENABLE</dt>
1883 <dd> 2298 <dd>
1884 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If 2299 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
1885defined to be <code>0</code>, then they are not.</p> 2300defined to be <code>0</code>, then they are not.</p>
1886 </dd> 2301 </dd>
1887 <dt>EV_STAT_ENABLE</dt> 2302 <dt>EV_STAT_ENABLE</dt>
1888 <dd> 2303 <dd>
1889 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If 2304 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2305defined to be <code>0</code>, then they are not.</p>
2306 </dd>
2307 <dt>EV_FORK_ENABLE</dt>
2308 <dd>
2309 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
1890defined to be <code>0</code>, then they are not.</p> 2310defined to be <code>0</code>, then they are not.</p>
1891 </dd> 2311 </dd>
1892 <dt>EV_MINIMAL</dt> 2312 <dt>EV_MINIMAL</dt>
1893 <dd> 2313 <dd>
1894 <p>If you need to shave off some kilobytes of code at the expense of some 2314 <p>If you need to shave off some kilobytes of code at the expense of some
1895speed, define this symbol to <code>1</code>. Currently only used for gcc to override 2315speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1896some inlining decisions, saves roughly 30% codesize of amd64.</p> 2316some inlining decisions, saves roughly 30% codesize of amd64.</p>
2317 </dd>
2318 <dt>EV_PID_HASHSIZE</dt>
2319 <dd>
2320 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2321pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2322than enough. If you need to manage thousands of children you might want to
2323increase this value (<i>must</i> be a power of two).</p>
2324 </dd>
2325 <dt>EV_INOTIFY_HASHSIZE</dt>
2326 <dd>
2327 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2328inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2329usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2330watchers you might want to increase this value (<i>must</i> be a power of
2331two).</p>
1897 </dd> 2332 </dd>
1898 <dt>EV_COMMON</dt> 2333 <dt>EV_COMMON</dt>
1899 <dd> 2334 <dd>
1900 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2335 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1901this macro to a something else you can include more and other types of 2336this macro to a something else you can include more and other types of
… …
1928the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2363the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1929interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2364interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1930will be compiled. It is pretty complex because it provides its own header 2365will be compiled. It is pretty complex because it provides its own header
1931file.</p> 2366file.</p>
1932 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2367 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1933that everybody includes and which overrides some autoconf choices:</p> 2368that everybody includes and which overrides some configure choices:</p>
2369<pre> #define EV_MINIMAL 1
1934<pre> #define EV_USE_POLL 0 2370 #define EV_USE_POLL 0
1935 #define EV_MULTIPLICITY 0 2371 #define EV_MULTIPLICITY 0
1936 #define EV_PERIODICS 0 2372 #define EV_PERIODIC_ENABLE 0
2373 #define EV_STAT_ENABLE 0
2374 #define EV_FORK_ENABLE 0
1937 #define EV_CONFIG_H &lt;config.h&gt; 2375 #define EV_CONFIG_H &lt;config.h&gt;
2376 #define EV_MINPRI 0
2377 #define EV_MAXPRI 0
1938 2378
1939 #include &quot;ev++.h&quot; 2379 #include &quot;ev++.h&quot;
1940 2380
1941</pre> 2381</pre>
1942 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2382 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
1947 2387
1948 2388
1949</pre> 2389</pre>
1950 2390
1951</div> 2391</div>
1952<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2392<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
1953<div id="COMPLEXITIES_CONTENT"> 2393<div id="COMPLEXITIES_CONTENT">
1954 <p>In this section the complexities of (many of) the algorithms used inside 2394 <p>In this section the complexities of (many of) the algorithms used inside
1955libev will be explained. For complexity discussions about backends see the 2395libev will be explained. For complexity discussions about backends see the
1956documentation for <code>ev_default_init</code>.</p> 2396documentation for <code>ev_default_init</code>.</p>
2397 <p>All of the following are about amortised time: If an array needs to be
2398extended, libev needs to realloc and move the whole array, but this
2399happens asymptotically never with higher number of elements, so O(1) might
2400mean it might do a lengthy realloc operation in rare cases, but on average
2401it is much faster and asymptotically approaches constant time.</p>
1957 <p> 2402 <p>
1958 <dl> 2403 <dl>
1959 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2404 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2405 <dd>
2406 <p>This means that, when you have a watcher that triggers in one hour and
2407there are 100 watchers that would trigger before that then inserting will
2408have to skip those 100 watchers.</p>
2409 </dd>
1960 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2410 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2411 <dd>
2412 <p>That means that for changing a timer costs less than removing/adding them
2413as only the relative motion in the event queue has to be paid for.</p>
2414 </dd>
1961 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2415 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2416 <dd>
2417 <p>These just add the watcher into an array or at the head of a list.
1962 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2418=item Stopping check/prepare/idle watchers: O(1)</p>
2419 </dd>
1963 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2420 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2421 <dd>
2422 <p>These watchers are stored in lists then need to be walked to find the
2423correct watcher to remove. The lists are usually short (you don't usually
2424have many watchers waiting for the same fd or signal).</p>
2425 </dd>
1964 <dt>Finding the next timer per loop iteration: O(1)</dt> 2426 <dt>Finding the next timer per loop iteration: O(1)</dt>
1965 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2427 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2428 <dd>
2429 <p>A change means an I/O watcher gets started or stopped, which requires
2430libev to recalculate its status (and possibly tell the kernel).</p>
2431 </dd>
1966 <dt>Activating one watcher: O(1)</dt> 2432 <dt>Activating one watcher: O(1)</dt>
2433 <dt>Priority handling: O(number_of_priorities)</dt>
2434 <dd>
2435 <p>Priorities are implemented by allocating some space for each
2436priority. When doing priority-based operations, libev usually has to
2437linearly search all the priorities.</p>
2438 </dd>
1967 </dl> 2439 </dl>
1968 </p> 2440 </p>
1969 2441
1970 2442
1971 2443
1972 2444
1973 2445
1974</div> 2446</div>
1975<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2447<h1 id="AUTHOR">AUTHOR</h1>
1976<div id="AUTHOR_CONTENT"> 2448<div id="AUTHOR_CONTENT">
1977 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2449 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1978 2450
1979</div> 2451</div>
1980</div></body> 2452</div></body>

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